Wariso took the fourth qualifying place in his semi-final in a time of 45.59, but the manner of his running was still far from reassuring following his misjudgement in the opening race, when he had looked round and slowed over the final 50 metres and missed the third automatic qualifying place to a fast-finishing opponent.
Yesterday he also disrupted his rhythm in the home straight by twisting round to survey the field, although on this occasion he secured the place he needed.
It has been an erratic competition so far for the man who was chosen for an individual place ahead of Roger Black, who is now observing the action from the high viewpoint of the BBC TV commentary point, having retired earlier this month.
But now he is in the final, where there is not going to be any point in taking measures apparently intended to conserve energy. And his times are moving in the right direc-tion.
In contrast to their 31-year-old colleague, Thomas and Richardson have progressed through two rounds with the minimum of anxiety.
Thomas, who has won only once in his six meetings with Richardson this season, albeit at the AAA trials, looked in impressive shape as he won his semi-final in 44.82sec, three places ahead of Wariso.
"Solomon is a bit of a wild card," he said. "So I went out hard over the first 300 metres and then waited to see what happened.
"I think the title is between Mark and myself. The proof's in the pudding now - it's too late for talking. At the end of the day it will be about who has the most strength left in their legs after the rounds. We'll find out tomorrow, and may the best man win.
"I won't be avoiding Mark before the final, but I won't be going over to him for a friendly chat. We both want to win." Richardson took second place in his semi-final behind Tomasz Czubak of Poland, who celebrated a national record of 45.22sec, with the Briton recording 45.51.
"I just wanted to be in the first two," Richardson said, adding that it was important to maintain concentration even when races were being run relatively slowly. The main challenge to Britain retaining a title they have held since 1986 is likely to come from the Poles, who saw Robert Mackowiak lower Czubak's record to 45.08sec behind Thomas in the second semi-final.
Allison Curbishley qualified easily for today's women's 400 metres final as she took second place in a time of 51.43sec behind Grit Breuer of Germany, who won the semi-final in 50.79. She will be joined there by Britain's other representative, Donna Fraser, who took fourth place in the other semi-final won by Hel-ena Fuchsova of the Czech Republic in 50.87. Fraser recorded 52.05sec.
Julian Golding made a promising start in the 200 metres, winning his first-round heat easing down in a time of 20.39sec, which was just 0.01 outside his personal best.
Katharine Merry, one of Linford Christie's training group alongside Jamie Baulch, Paul Gray and the newly-installed European champion Darren Campbell, maintained the mood of celebration in the camp with an assured performance in her opening heat of the 200 metres.
Merry kept her form over the final 50 metres to move through from fourth to second place behind Ukraine's world champion, Zhanna Pintusevich, who recorded 23.02. Merry, clearly satisfied with her run, was timed at 23.23.
However, the pace proved too much for Sarah Wilhelmy, the 18-year-old world junior bronze medallist now coached by Bruce Longden, who previously guided the career of another Essex girl, Sally Gunnell.
Wilhelmy, who finished the indoor season top of the world rankings with 23.54sec, faded over the last 40 metres after she had entered the final straight in one of the four first places.